The present invention relates to a lubricating system for an engine having a vertical shaft, and more particularly to a system for lubricating a big end of a crankshaft of the engine.
Generally, a vertical shaft engine can not use an ordinary lubricating system where oil in an oil reservoir provided in a crankcase is scooped up with a crankshaft for lubricating the engine. Consequently, the vertical shaft engine is employed with a lubricating system having an oil pump. Japanese Utility Model Application Laid-Open 62-105312 discloses a lubricating system for the vertical shaft engine in which an oil pump is provided in an end of a balancer shaft. An outlet port of the oil pump is communicated with openings of an oil supply passage formed around a lower portion of the crankshaft through an oil passage provided in the crankshaft. The oil passes to the big end passing through the passages.
The oil passage in the crankshaft is formed by combining several bores drilled in the crankshaft. Consequently, several manufacturing steps are necessary for forming the oil passage. Further, an end of the oil passage must be closed by a plug, which increases the manufacturing cost.
In another lubricating system in which lubricating oil is dropped only to bearings from openings. By this system other particular portions such as a magneto, cam bearings, pistons and tappets are not sufficiently lubricated.